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        //1.绝对值方法
        console.log(Math.abs(1));  //求绝对值
        console.log(Math.abs(-1));
        console.log(Math.abs('-1'));   //隐式转化，把字符串的-1转换为数字型
        console.log(Math.abs('pink'));  //NaN

        //2.三个取整的方法
        // 1)Math.floor()向下取整 往小的取值
        console.log(Math.floor(3.1));  //3
        console.log(Math.floor(3.5));  //3
        console.log(Math.floor(3.9));   //3

        //2)Math.ceil()往上取整，往大的取
        console.log(Math.ceil(3.1));//4
        console.log(Math.ceil(3.5));//4
        console.log(Math.ceil(3.9));//4

        //3)Math.round()四舍五入  ,其它数字都是四舍五入 .5是往大的取 (负数，五舍六入)
        console.log(Math.round(3.1));//3
        console.log(Math.round(3.4));//3
        console.log(Math.round(3.5));//4
        console.log(Math.round(3.9));//4
        console.log(Math.round(-1.1)); //-1
        console.log(Math.round(-1.5));//-1    负数：五舍六入
        console.log(Math.round(-1.6));//-2

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